Here’s further proof that in radio, even the smallest change can ruin a project.
I bought a 2.5m mast a month ago, but I didn’t get around to working on this because of the intense and continuous heat this summer in Barcelona.
Last night I finally did it. I didn’t change the antenna, I didn’t change the cable, I just moved the antenna structure from one side to the other.
In this way the antenna has been raised 1.5m. Well, the range has improved, which made me happy, but looking at Graph1090, I noticed something very strange in general. I’ve attached screenshots.
My suspicion is that perhaps without realizing it, I pulled on the cable, damaging the connector. That’s the only thing it could be; nothing else makes sense. What do you think?
Well, next monday I’ll go to a ham radio shop in Barcelona and buy new LMR-400 cable and ask them to install the connectors there.
The current cable is RG213. It’s 25 years old and for 15 years it was rolled up and lying on the roof floor of my building, so obviously it wasn’t in very good condition anymore.
Although it has worked very well until now, what is happening now has made me decide to change the cable.
The location before the change does not seem to bad, so maybe there is only a small improvement to be made.
Or even maybe none, if you do not have a clear horizon and the higher antenna does not help you overcome obstacles that are close by?
What type/make of antenna are you using, it is hard to judge seeing the pictures, but it does not seem like the common length like eg. the FA antenna with 66cm.
The location is good: a tall building, my apartment is on the top floor, the penthouse, and everything is set up on the terrace. The antenna extends 3 meters above the building’s roof.
The only drawback is a massive building nearby (wide and very tall).
You can look this:
It’s not a commercial antenna, it’s a homemade dipole. It’s inside the last section of the PVC pipe. I’ve attached a photo from before the soldering:
It’s made with a 6mm thick aluminum tube, protected with XPS to prevent any movement. All inside a PVC radome.
On top of this there is another piece of xps that encloses the entire antenna and solder joints.
This type of material (XPS and similar) does not affect reception because it is composed of 98% air.
Now I’m going to check the connector in case it looks damaged. Anyway, everything should be fine on Monday with the new cable.
The connector might be damaged . To check this, use a multimeter to see if there is at least continuity between the ends (shield and center pin/connector). I would simply re-crimp the connector or replace it with a new one. As for the LMR400, I would stick with the RGC213 and buy a 1090MHz antenna—whether from FlightAware, RadarBox, Vinnant, or even AliExpress. Depending on the quality of your DIY antenna, the gain with a new antenna would likely be higher.
The cable is very old, and having spent 15 summers in the sun, I don’t trust it to work properly.
I’ll go get the new cable on Monday and install it; that’s decided.
I would stick with the RGC213 and buy a 1090MHz antenna
Hahaha, I’ve been tinkering with all kinds of antennas since I was young. For me, it’s more satisfying to see that an antenna I’ve made myself performs well. Having everything done takes all the excitement out of the hobby.
It’s true that some commercial antennas have more gain; a dipole doesn’t add more than 2 dB, but if the rest of the setup is optimal (cable length, type of cable, location, etc.), it’s worth more than someone who has the best antenna but uses it incorrectly.
I’m never going to buy an antenna; that would make me get bored with this ADS-B hobby.
Yes, I checked it and everything seemed fine.
It’s likely the problem is intermittent, that the connection is weak now.
I won’t worry about it anymore until Monday when I get the new cable with new connectors.
While I was taking the antenna off, I also replaced the mast mounts.
Well, I installed the connectors myself. The cable was from an old 11m DX station and had the classic PL connectors.
Being outdoors, it was affected not only by the strong sun but also by the rain over the years, which can seep in through the connectors and degrade the cable. When I cut it, I saw that the shielding and the center conductor were in good condition, but I was surprised that the dielectric in the center conductor was extremely easy to cut. It’s definitely in bad shape, and any tug yesterday could have damaged it.
I have Four RPi’s running 4 ADS-B Receivers:
I’m planning to do something like this.
I would buy an identical dongle and use it to test and compare antennas.
As for AIS, when I come by train from Calella or Mataró I see a long queue of ships like cruise ships and many cargo ships waiting to enter the port of Barcelona.
I’d like to experiment, but my house is about 2 km from the sea, and for example, the Diagonal Mar skyline in Barcelona would block quite a bit of the signal in that direction. I don’t think it would work well for me.
Ok, the way I have done it is with an RTL-SDR dongle tuned to ATC, rtl_fm running on the RPi, and use netcat (nc) to send audio over the LAN to a Mac that has nc and sox on it.
The reason for asking about this is, the above works but the audio quality is not very good. On most transmissions I hear a sidetone. Some transmissions you only hear the tone. Wonder if you see a similar thing with your setup.
I was thinking maybe I’m getting interference from the FM broadcast band since this is just below the airband (88 to 108 MHz). I tried a FM notch filter, but it didn’t help at all. So, just curious about what experience you have had.
My apartment is about 3 kM from lake Ontario coast line, and there are lot of high tise buildings between my building and lake ontario coast line. Still I am able to track about 30 to 45 ships & boats.
I never heard a side tone. You can go to my site of aggregator AirNav which I linked above and listen to it for say 15 minutes toget an idea. The Toronto Pearso closes for traffic at mid night till early morning. So best time to hear is from 10am Eastern time to 9 pm Eastern time.
For your reference I am posting below the config file for RTL-Airband installed by debian package as per detailed REDME at my Github site linked above.
NOTE: I had to install icecast on RPi to enable sending audio on LAN & Web.
cat /etc/airband/rtl-airband.conf
# Scanning mode example
# Single dongle, three frequencies, output to Icecast server and to a file.
# Refer to https://github.com/rtl-airband/RTLSDR-Airband/wiki
# for description of keywords and config syntax.
devices:
({
type = "rtlsdr";
#index = 0;
serial = "00000001";
gain = 25;
correction = 30;
mode = "scan";
channels:
(
{
freqs = ( 118.350, 118.700, 124.450, 132.800 );
labels = ( "Tower-South", "Tower-North", "Approach-1", "Approach-2" );
outputs: (
{
type = "icecast";
modulation = "am";
server = "127.0.0.1";
port = 8000;
mountpoint = "stream.mp3";
name = "Tower + Approach";
genre = "ATC";
description = "CYYZ Toronto - aggregated feed";
username = "source";
password = "hackme";
send_scan_freq_tags = false;
},
{
type = "icecast";
server = "audio.rb24.com";
port = 8000;
mountpoint = "EXTVHF000597";
name = "Tower + Ground + Approach";
genre = "ATC";
description = "CYYZ Toronto - aggregated feed";
username = "XXXX@example.com";
password = "XXXXXX";
send_scan_freq_tags = false;
}
#{
# type = "file";
# directory = "/home/pi/recordings";
# filename_template = "TWR+GND+APP";
#}
);
}
);
}
);
Even the best PL/ SO connectors aren’t rated for GHz.
If you feeder was intended for 11m, the insulation in the connectors is probably the brown phenolic resin (?). Also, there are no seals to keep the water out. You can get around the ‘seal’ problem by using self-amalgamating tape, but for ADS-B, you should start with N-Type connectors.
Typically RG213 has polyethylene dielectric, but if it’s very high quality, it might have PTFE dielectric which is much easier to cut.
“Real” RG213 (as opposed to improved options) has a surprising low frequency range.
(expect 8.5dB loss per 100’ at 1100MHz)
Apparently, our fellow forum member was satisfied with his system, so the cable itself shouldn’t have been the problem. That’s why I suggested simply redoing the connectors and swapping the antenna for one with better sensitivity and gain. The issue for him was that his DIY antenna couldn’t be replaced, as it was an object that gave him satisfaction.
Another point I want to highlight is that, depending on the installation height, raising it by another meter or two will result in practically no increase in the number of messages or aircraft.
Regarding height, there are two types of scenarios: an antenna in an elevated location and an antenna in a low location or installed indoors.
If you have an antenna installed on a tower, a hill, or a very tall building, raising it by one or two meters yields no noticeable gains (unless there is a very close obstruction, such as a neighboring building). On the other hand, if your antenna is installed at the height of a chimney, roof, or garage, raising it another two or three meters can significantly increase its range.
I apologize if I failed to be clear in my previous arguments.
I disagree. On other bands, if the antenna is tall and well-positioned, an extra meter doesn’t make much of an improvement, but on ADSB, where reception requires a direct line of sight, an extra meter does improve the range.
